it ON ANIMAL LIFE We 
moths are mottled so as to mimic the bark of 
trees, or moss, or the surface of stones. One 
beautiful tropical butterfly has a dark wing 
on which are painted a series of green leaf 
tips, so that it closely resembles the edge of 
a pinnate leaf projecting out of shade into 
sunshine. 
The argument is strengthened by those’ 
cases in which the protection, or other advan- 
tage, is due not merely to colour, but partly 
also to form. Such are the insects which 
resemble sticks or leaves. Again, there are 
cases in which insects mimic others, which, for 
some reason or other, are less liable to danger. 
So also many harmless animals mimic others 
which are poisonous or otherwise well pro- 
tected. Some butterflies, as Mr. Bates has 
pointed out, mimic others which are nauseous 
in taste, and therefore not attacked by birds. 
In these cases it is generally only the females 
that are mimetic, and in some cases only a 
part of them, so that there are two, or even 
three, kinds of females, the one retaining the 
normal colouring of the group, the other 
mimicking another species. Some spiders 
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